Solving trusses with the Direct Stiffness Method

[Diego Saenz]

I'm creating a computer implementation to solve planar trusses. And I'm not sure how to check if the truss is solvable or not. Can you help me with that?

In my implementation, the trusses are created randomly (needs to be this way), so i get a lot of unstable or indeterminate trusses. I want to discard bad trusses without calculating the determinant of the stiffness matrix or trying to solve them.

Is this condition enough to discard such trusses? If I filter the trusses with this criteria, will i lose some good ones? ----> 2j = m+r

j - number of joints
m - number of members
r - number of reactions

Thanks.

 

[nvn]

If I filter the trusses with this criterion, will I lose some good ones? ----> 2j = m+r

Diego Saenz: Yes, you would lose some good ones. Instead, discard only the trusses having 2*j > m + r. Keep the trusses having 2*j ≤ m + r.